It is well known that many characteristics or features of a tire may impact its performance, wear, noise generation, and the like. Over the years, various types of analyses have been performed on tires. There has been the monitoring of the actual physical operation of the tire as upon a rotating drum or the like. Analytical testing of external and cross sectional features of the tire have also been undertaken.. More recently, it has been known to analyze the contact patch or footprint of the tire as it makes contact with road or loading surface to determine therefrom various structural and operational characteristics thereof. Those skilled in the art understand that a tire footprint constitutes the image of the tire imparted upon a planar contact surface when the tire is inflated to a set pressure and receives a predetermined load.
In the prior art, such tire footprints were generally analyzed manually. In one such method, ink was applied to the tire surface which was then loaded onto a planar substrate such that the ink would be transferred from the tire to the substrate. In most instances, the substrate constituted paper or another suitable thin sheet material. The image of the tread and other contact areas of the tire would dry upon the paper, at which time the areas of the substrate having ink thereon would be cut out of the substrate and weighed. In similar manner, the uninked area portions of the substrate would also be weighed. A comparison of the two weights would provide the ratio of the tread or contact areas to the void areas of the footprint image. It was also known that the inked footprint image could also be used to physically measure the footprint width, and to similarly measure the individual rib lengths of the footprint. The length relationships of the several ribs can then be compared and the general shape of the footprint can be characterized.
The prior art technique for footprint analysis was labor intensive and prone to error. The significant implementation of human participation in measurements, calculations, and decisive judgment gave rise to inconsistencies and errors in the analysis. Accordingly, there is a need in the art for a method and apparatus for video imaging of tire footprints which provides a wide range of data, which is based upon a digital data analysis, and which allows for computerized calculation of the footprint shape data.